Okay. Problem Solved.
For anyone else having this same problem or a similar problem...
do the following:
1) download the Avast setup from the website:
http://www.avast.com/de-de/download-software2) and the Avast Cleanup tool:
http://files.avast.com/iavs9x/avastclear.exe3) also download Rajzor's Cleanup Tool from here:
http://rejzor.wordpress.com/avast-cleanup-tool/uninstall Avast in normal mode from Software or Programs and Features. Then boot into Safe-mode (use the F8 Key during boot-up, select Safe-mode with network).
When in Safe-mode use the avast cleanup tool from avast. select the proper Version in selection menu and continue till done.
Reboot, this time into normal mode. Then use Rajzors Cleanup Tool. It removes everything else that was left from an old installation.
Now start the new Installation of Avast. then reboot again.
In my case the problems were resolved. It seems it wasn't directly a problem in the new build 2011. It must have been some changes in registry entries or mismatched file versions from the other builds.
One more thing. I use Avast in its standard default configuration. I have never changed any of the special settings. In its default, Avast works great.
Thanks to you all for your help.
*** NOTE: this happened on a freshly installed Window 7 x64 Notebook. The Avast 2014.2009 version auto updated to 2014.2011 and wham, the problem was there. This build needs a lot more bug checking...